1 files changed, 67 insertions, 0 deletions
diff --git a/scope.moon b/scope.moon
new file mode 100644
index 0000000..a72a606
--- /dev/null
+++ b/scope.moon
@@ -0,0 +1,67 @@
+import Const, Op from require 'base'
+
+ancestor = (klass) ->
+  assert klass, "cant find the ancestor of nil"
+  while klass.__parent
+    klass = klass.__parent
+  klass
+
+local Scope
+
+constify = (val, key) ->
+  typ = switch type val
+    when 'number'
+      'num'
+    when 'string'
+      'str'
+    when 'table'
+      if base = rawget val, '__base'
+        -- a class
+        switch ancestor val
+          when Op
+            'opdef'
+          else
+            error "#{key}: cannot constify klass '#{val.__name}'"
+      elseif klass = val.__class
+        -- an instance
+        switch ancestor klass
+          when Op
+            'op'
+          when Const
+            return val
+          else
+            error "#{key}: cannot constify '#{klass.__name}' instance"
+      else
+        return Scope.from_table val
+    else
+      error "#{key}: cannot constify Lua type '#{type val}'"
+
+  Const typ, val
+
+class Scope
+  new: (@node, @parent) =>
+    @values = {}
+
+  set_raw: (key, val) => @values[key] = constify val, key
+  set: (key, val) =>
+    @values[key] = val
+
+  get: (key) =>
+    if val = @values[key]
+      return val
+
+    if val = @parent and @parent\get key
+      return val
+
+    part, key = key\match '^(.-)/(.*)'
+    return unless part and key
+    scope = assert (@get part), "no such scope: '#{key}'"
+    scope\get key
+
+  from_table: (tbl) ->
+    with Scope!
+      .values = { k, constify v, k for k,v in pairs tbl }
+
+{
+  :Scope
+}